Droplet impact onto textiles: Wetting, spreading, and lamella-controlled splashing.

内容摘要

Textile weave structure, surface roughness, wettability, and liquid viscosity play a role in droplet spreading and the splashing behavior on commercial textiles following impact. We hypothesize that, collectively, these parameters define whether the droplet undergoes smooth spreading or splashing. In our experiments, we visualize the impact dynamics of droplets on textile samples. Experiments were conducted on eight commercial textiles featuring satin and plain weaves. Here, we used three Newtonian fluids (water, silicone oil, and a 45 wt.% aqueous glycerol solution) to investigate the post-impact behavior. High-speed shadowgraphy captured the impact at 30,000 - 50,000 frames per second. Fresh textile samples were used for each experiment to prevent contamination. In line with past works, textile samples were affixed to glass substrates to facilitate the visualization of surface-level spreading and splashing dynamics. Surface topography was quantified using high-resolution optical profilometry, revealing nearly an order of magnitude variation in root-mean-square roughness (Rrms), ranging from 4 to 35 &#x3bc;m. Impact velocities ranged from 1.00 to 2.98 m/s, with 3 repeats per condition. Image analysis was used to quantify spreading speeds and diameters. The droplet behavior was classified into spreading or splashing, depending on whether the droplet fragments following impact. Satin weaves promoted Cassie-Baxter wetting with high advancing and static contact angles (&#x3b8;max&#x2248;130 and &#x3b8;static>115 degrees), while plain weaves favored Wenzel wetting (&#x3b8;max&#x2248;121 and &#x3b8;static<100 degrees). Splashing thresholds for water decreased linearly with root-mean-square roughness (Rrms), but viscous fluids (e.g., silicone oil) showed roughness-insensitive splashing. Directional splashing emerged in satin weaves due to warp-aligned floats. An Ohnesorge-number-based scaling model unified critical splashing velocities across all textiles and fluids. These findings inform the design of performance textiles for forensics, medical coatings, and waterproofing applications.